using System;
using System.Collections;

using Org.BouncyCastle.Math;

namespace Org.BouncyCastle.Asn1.X509
{
	public class DsaParameter
		: Asn1Encodable
	{
		internal readonly DerInteger p, q, g;

		public static DsaParameter GetInstance(
			Asn1TaggedObject	obj,
			bool				explicitly)
		{
			return GetInstance(Asn1Sequence.GetInstance(obj, explicitly));
		}

		public static DsaParameter GetInstance(
			object obj)
		{
			if(obj == null || obj is DsaParameter)
			{
				return (DsaParameter) obj;
			}

			if(obj is Asn1Sequence)
			{
				return new DsaParameter((Asn1Sequence) obj);
			}

			throw new ArgumentException("Invalid DsaParameter: " + obj.GetType().Name);
		}

		public DsaParameter(
			BigInteger	p,
			BigInteger	q,
			BigInteger	g)
		{
			this.p = new DerInteger(p);
			this.q = new DerInteger(q);
			this.g = new DerInteger(g);
		}

		private DsaParameter(
			Asn1Sequence seq)
		{
			if (seq.Count != 3)
				throw new ArgumentException("Bad sequence size: " + seq.Count, "seq");

			this.p = DerInteger.GetInstance(seq[0]);
			this.q = DerInteger.GetInstance(seq[1]);
			this.g = DerInteger.GetInstance(seq[2]);
		}

		public BigInteger P
		{
			get { return p.PositiveValue; }
		}

		public BigInteger Q
		{
			get { return q.PositiveValue; }
		}

		public BigInteger G
		{
			get { return g.PositiveValue; }
		}

		public override Asn1Object ToAsn1Object()
		{
			return new DerSequence(p, q, g);
		}
	}
}
